Under Covers
by beatingoutasamba
Summary: Beckett attempts to infiltrate a high-class escort service suspected of murder, but Castle and Beckett get more than they bargained for when the head of the agency asks her to "audition". Set between 3x13 and 3x24. Chapter 2 has a hard M rating.
1. Chapter 1

**A/N: **I wrote this a long time ago, back when season three was airing, and I just rediscovered it. This is set sometime between "Knockdown" and "Knockout". Now, this chapter was actually chapter six of the original story, but I don't like the other chapters, so I've adapted two of them to be a stand-alone story. I couldn't let this smut waste away in some corner of my computer collecting dust. It needs to be read!

**Disclaimer: **_Castle _belongs to Andrew Marlowe and ABC Studios, not me.

* * *

Castle looked up from his barstool perch just in time to see Beckett come in from the outside. He nearly had a heart attack when he saw what she was wearing. She sparkled as the light glinted off of her short metallic grey dress. The bottom of her dress ended on her upper thigh, showing off her beautiful long legs as she sauntered closer to the bar, swaying her hips with the hypnotizing elegance of a ballerina. Castle paused for a minute to admire the provocative v-neck which didn't leave much to the imagination. As his eyes continued to travel over her exquisite body, he took in every detail – the way her wavy hair glimmered as she tossed it back, the long sleeves which only served to draw attention to her well-manicured hands, the oversized ring on her right index finger, her silver clutch… But what Castle gazed at the most was Beckett's face. Green eye shadow accentuated her _gorgeous _eyes and peony lip gloss made her lips look so inviting that Castle had to fight the urge to walk over and plant a possessive kiss on them. Her 4-inch silver heels clicked on the marble floor as she walked into the bar, her stunning eyes meeting Castle's for a brief moment. She threw a sly smile his way before turning around and sliding into a seat opposite the chief of surgery.

Finally exhaling the breath he didn't know he was holding, Castle did a flawless John Stamos impression, quietly exclaiming "Have mercy!" to the bartender. Then he downed the rest of his single malt scotch and tapped into his vivid imagination, dreaming about the day when he would see what was under the dress.

* * *

"I think he likes you," the chief said to Beckett as she sat down across from him.

"What?" she asked, genuinely confused.

"The guy at the bar who can't stop staring! Not that I blame him, you are quite a beauty! I think I made the right choice in recruiting you."

Under Castle's intense scrutiny, Beckett began to blush. Then, shaking her head to clear her mind, she said "Don't forget, you haven't recruited me yet."

"What do you want to know?"

Beckett bombarded him with questions, all of which he answered with ease and charm. _He's really good at this… If I wasn't a cop, I'd almost consider moonlighting, _she thought. The chief continued to prattle on about the benefits of being a high-class escort until Beckett stopped him.

"Okay, I'm sold. What do I have to do?"

"Well, I can't just let you into the agency; you're going to have to prove yourself."

Beckett was glad she had the foresight to have Castle sitting in the bar. It would have been awkward to flirt with someone else.

"And how, might I ask, do I prove myself?"

"Normally the agency would pick your clients for you, but we need to know that you have what it takes. Think of this as an 'audition'. Pick up a man in this bar. Enchant him; make him want to pay for you." The chief discreetly handed her the key to a hotel room. "Take him up to room 308 and give him the time of his life. Then take his money and meet me back at the hospital tomorrow."

"And how much does a night with me go for these days?"

"$3,000. If you can't get a man to pay that much for you, then we don't want you in the agency."

"I'll bet I have that man in bed before sundown," she challenged, gesturing to Castle.

"You're on. Now show me what you've got."

* * *

Castle inhaled sharply as Beckett stood up from the booth and started walking towards him.

"Hey," she said seductively. "Buy me a drink?"

"But, I don't even know your name," he teased.

"I'm Katherine," she said, drawing out each syllable. Upon hearing her husky voice, Castle's breathing quickened. He hadn't realized exactly how much power she had over him until this very moment.

"I'm Rick," he replied.

"Okay, now that we're acquainted, how 'bout that drink?" Beckett asked, moving onto the barstool next to Castle. She took her index finger and began to run it over his chest in playful circles and smiled when she felt Castle's heartbeat grow faster.

He ordered drinks for them both and then sat back to look at Beckett. "So, Katherine, what brings you here this evening?"

"Actually, I think I found what I was looking for," she said, loud enough for the chief to hear. Then she leaned in close to Castle, putting her mouth by his ear. He stiffened as her warm breath grazed his cheekbone. The chief presumed she was discussing her fee, what she really said was, "Ryan, Esposito, have you got a trace on his phone?" she whispered.

Castle had forgotten about the microphone in his shirt collar, so her words surprised him. Then, drawn out of his undercover fantasy, he began to play along. Turning the tables on Beckett, he put his hand on her bare knee.

"Yeah, we're linked into his phone. We see everything he does. If the chief contacts his boss, we'll know about it," Ryan's voice said into their ears.

Beckett found it hard to concentrate on the case with Castle's hand caressing her knee. Shivers ran up her spine as his nimble fingers went higher and higher up her leg.

"Good, let us know if he does anything suspicious," she managed to whisper. Then, returning to the task at hand, she pulled away from Castle.

"You know, why don't we forget the drinks and take this party upstairs?" Beckett asked him, dangling the room key in front of his face.

Much to her dismay, Castle removed his hand from her knee. Standing up, he held his arm out to her and said, "Shall we?"

She took his arm and they walked out of the bar towards the elevator. Once they were safely inside the metal box, they separated. Neither one of them wanted to admit that they missed the other's touch, so they stood there in silence and listened to the elevator music.

Beckett wished that this was real. She wished that they were going upstairs to do _more_ than sit in the hotel room and talk. Castle was wishing the same thing, but he knew it would never happen. Beckett had made it perfectly clear that she just wanted to be friends and what she said next just confirmed it.

"Remember, we are just going to _sit_ in the hotel room. If you try anything, you will be going to a very special level of Hell. A level reserved for child molesters and people who talk at the theater. And you know I can make it happen." She hadn't wanted to say that, but with Ryan and Esposito listening to their every word, she had to keep up appearances.

"Don't worry, I'll be the perfect gentleman," Castle said resignedly, exiting the elevator on the third floor.

* * *

Ryan and Esposito were sitting in the van watching computer monitors when one of them started to flash.

"What's going on?" Ryan asked Esposito.

"There's some activity on the chief's phone. It looks like he's connecting to something."

"What?" Ryan asked impatiently.

"A video feed of a hotel room," Esposito responded, a little confused.

"Why would he connect to a video feed?"

"I don't know. Wait…" They watched in shock as Castle and Beckett appeared on the streaming video.

"Oh god," they said in unison.

* * *

"There's a camera in the room! The chief's watching you!" Ryan yelled into the microphone.

There was no time to think, so Beckett improvised. She launched herself at Castle, attacking his lips with her own. He was slightly stunned, but recovered quickly, passionately kissing her back. His tongue left a searing trail of fire along her bottom lip, teasing her mouth open. She writhed under his body and splayed her hand across his back, holding onto him for dear life, as if at any moment she would wake up and discover that it was all a mirage. A low moan escaped Beckett's lips as three years of sexual tension was released.

Breaking away for air, Castle stared at the ravishing woman beneath him, not daring to believe she was real. He moved closer to her until they were millimeters apart and recognized the lust that was clouding her eyes. This was more than another undercover kiss. She wanted him. So, he ran his hand over her defined jawbone and lowered his mouth to fleetingly kiss her lips.

"I'm gonna go to the special hell," he muttered breathlessly.

* * *

**A/N: **The follow-up chapter will be posted in a day or two. I just want to fix a few things.


	2. Chapter 2

**A/N: **Because I'm an awesome person, I fixed this chapter up as fast as possible so I could post it today. Fair warning, it is very smutty, so if you don't like that sort of thing, don't read it. I hope you like it!

* * *

"Did she just—"

"Yeah, she did."

They gaped at the screen for a moment more, before Esposito finally broke the silence. "Pay up."

Ryan handed him a twenty dollar bill and turned back to the screen. Not realizing that he was speaking into the microphone, he said, "Man, they're really goin' for it! Think they'll go all the way?"

To answer his question, Beckett whispered into Castle's shirt collar. "Ryan, if you watch this, I will kill you in your sleep. But before you guys go dark, tell me one thing – is there any indication that the chief can hear us?"

"Uh… no. As far as we can tell, all he has is a visual," Esposito replied.

"Okay. Keep monitoring his cell. We'll contact you when we're— we'll contact you in a few hours."

Ryan and Esposito snickered.

"Well have fun you two!"

"Castle, we want her home by midnight."

"Ryan, so help me, if you don't—"

"Going dark now!" they both said hurriedly, shutting off all of the monitors.

They stared slack-jawed at the now-blank computer and then exchanged knowing glances, each seemingly reading the other's mind.

Esposito got out his phone and opened a new text message.

"Hey Lanie, you'll _never_ guess what just happened…."

* * *

"Rick," Beckett murmured against Castle's lips. "Are you sure you're okay with this? I mean, we are being watched, and if you're not comfortable with that, we can—"

Castle put his finger to her lips. "Shh…" he said. "Forget about me. Are _you_ okay with this?"

Beckett smiled. It was very thoughtful of Castle to consider her feelings, especially after the way she had thrown herself at him not two minutes before, but she wanted this more than life itself, and she had to make that perfectly clear.

Kate whispered into his ear. "If I wasn't sure, would I be doing this?"

He gasped as she lightly bit his ear, pulling at it with her teeth. He merely shook his head in response, his ability to speak having been temporarily disabled by her tongue darting out to taste the sensitive skin of his neck.

"Glad we're on the same page. Now let's put on one hell of a show," she breathed.

* * *

Beckett slipped her hands underneath Castle's formal jacket and gently slid it off and dropped it on the floor. Then she ran her hands over his body and began to unbutton his shirt, peppering light kisses on the newly revealed skin of his chest. He drew in a deep breath as she went lower. All of his fantasies were finally coming true. In fact, the whole experience was so surreal that he was still having trouble believing that it was actually happening. Kate Beckett was going to sleep with him. Kate Beckett was removing his clothing. Kate Beckett was- _Oh my God! _ Her wandering hands were going _much_ farther than the last button of his shirt. Was she trying to kill him?!

To keep himself from losing it on the spot, Castle swept her off her feet, causing her to burst into a fit of laughter. She put her arms around his neck and smiled up at him.

"I'm really glad we're doing this," she said quietly.

"Me too," he replied, leaning forward to kiss her.

Rick carried her to the bedroom and set her down at the foot of the king-sized bed. Moving behind her, he wrapped his arms around her body and held her for a moment, breathing in her scent.

"You smell like cherries," he whispered for the second time.

He brushed over Kate's erect nipples and lightly pinched them through the silver fabric, sending blissful shivers down her spine. His hands glided over her smooth shoulders until they reached the zipper at the back of her dress. He hesitated for a moment, but one moan from Kate was enough to convince him to continue. He lowered the zipper at an excruciatingly slow pace because he wanted to savor every second of their night together, and as more and more of her pale back was exposed, he realized that she wasn't a dream. For the first time that night, he was absolutely positive that this was real.

Unzipping the final inch, he let her dress fall to the floor around her ankles. She was a vision in high heels and black lingerie panties. He couldn't help but stare.

Noticing a mark on her lower back, he said, "So… a dragonfly huh?" He had wondered about her tattoo for a year and just had to comment.

Kate simply nodded and turned around to face him. She felt very exposed, partly because of her state of undress, and partly because of the camera, but she discovered that the combination turned her on. She had never had an audience before, and she found it surprisingly thrilling.

Castle tentatively reached out to touch her soft breast and she bit her lip in pleasure. A moan escaped her throat as he took her nipple in his mouth and ran his tongue over the sensitive nub. Trailing his tongue over her body in lazy figure eights he went lower and lower until he reached the black lace. He slipped his thumbs under the fabric and slid the panties down, finally revealing what he desired most. Kate bucked against his hand when he found her clit. The friction was almost too much to bear, and he wasn't even inside her and when his fingers felt her wetness and entered slightly, she nearly came on the spot. He laughed and withdrew his hand, sucking her sweet juices from his fingers and then kissing her. She tasted herself on his tongue before he pulled away, leaving her breathless for more.

"I need you in me," she whimpered out of desperation.

Castle smiled. He had reduced the levelheaded detective to a pile of mush with one brush of his hand. But, as much as he wanted to throw her on the bed and fuck her senseless, she was going to have to be patient. He didn't want a one-night stand. He wanted a lifetime. But, in case he couldn't have that, he was determined to make this night last a lifetime.

He gently lowered her onto the bed and she watched as he removed the rest of his clothing, her eyes devouring the view.

A few moments later, Castle climbed on the bed and crawled towards her. Kate sighed when his hands grazed her inner thigh and moaned when he replaced his fingers with his lips, trailing kisses over her smooth legs. The feel of his mouth on her skin was delightful. Teasing her, he quickly passed his tongue over her sensitive clit before returning to her thigh. Her hips involuntarily jerked upwards as pleasure shot through her body from the unexpected movement.

"Castle, please…" she murmured, barely recognizing her own begging voice.

He couldn't resist giving her more, so he took her clit in his mouth and stroked it roughly with his tongue. She arched her back in response and grabbed his hair in her hands, holding him to her heat. He went faster and faster, drawing cries of ecstasy from the woman beneath him. And when he knew she was impossibly close, he slowed his rhythm to almost nothing, keeping her just out of reach. She closed her eyes and waited for release, and just when she thought he would never let her come, he quickened his tongue's rhythm and pushed two fingers inside her. These actions combined sent her over the edge into oblivion and she screamed his name in pleasure. She shook and quivered, tingling all over from the intense orgasm exploding within her and as the aftershocks racked her body, Kate knew that they could never go back to the way things had been before. This night couldn't be ignored or forgotten, and she was perfectly fine with that.

"Now it's your turn," she said simply and before he knew what was happening, she flipped him over with ease and cuffed him to the bedpost.

"Where did you-? What?" Castle stuttered.

"I had them in my clutch, in case I needed to arrest somebody, but I seem to have found a new use for them."

"I think you just enjoy cuffing me," he smirked.

"Well… maybe," she winked. She loved to feel in control, which was one of the many reasons she loved her job so much. Arresting criminals was incredibly satisfying… _As is my current activity_, she thought.

She trailed her tongue over his chest, going lower and lover before grinning diabolically.

All Castle could do was watch as she took his entire length into her mouth. He moaned in pleasure as she ran her tongue down his shaft. He didn't know how much longer he could last under her ministrations. He bucked against her mouth as she lightly kissed the head of his shaft before pulling a condom from out of nowhere and he stared in disbelief as she proceeded to pull the condom over his length – using only her mouth. It was without a doubt one of the sexiest things he had ever seen.

"When did you—I mean, how did you do that?" he asked in wonder.

"Oh Castle, that is one of the many things for me to know and you to never find out."

Then, in one swift movement, she lowered herself onto him and whatever confusion he might have felt disappeared as he felt her tight walls clench around his shaft. He reveled in the feeling of being totally surrounded by her wet heat; they seemed to be made for each other. His hands were still trapped by her handcuffs, so he thrust his hips upward to meet her body, and every time she slammed herself down onto him, he seemed to go deeper and deeper. He could feel the pressure building within him and he tried to increase their passionate rhythm. They wordlessly gazed at each other, enraptured by the sexual hunger in each other's eyes. Kate pinched his nipples before finally releasing him from the cuffs, knowing that the final outcome would be ten times better as a two-person tango.

Pleasure came at her from all angles when he used his newly freed hands to knead her breasts and rub her clit. Completely taken over by lust, they abandoned all hope of stopping. All it took was two more thrusts to make the tingling in her toes work its way to her feminine heat and explode into fireworks of ecstasy. She shuddered and arched her back involuntarily as she violently climaxed on top of him.

The delicious friction of their bodies being joined together was too much to bear. One look at Beckett's glowing face was all Castle needed to send him skyrocketing over the edge. He quivered with release and collapsed on the bed, taking her with him.

* * *

Too exhausted to say anything, they pulled the covers over their bodies and snuggled together. They felt a much closer bond and knew that their relationship would never be the same. Kate smiled into Rick's chest and lightly kissed his lips before falling into a deep and contented sleep.

Castle looked down and the gorgeous detective by his side and grinned. He tenderly kissed her hair and closed his eyes. Life had ended as they knew it

* * *

**A/N: **I'm glad this story got to see the light of day once more. This is the final chapter, but if enough people want me to, and if I manage to find the time to do it, I might be convinced to write the morning after as well. Well, it's time for me to get back to NaNoWriMo! I'm working on an amazing 45-chapter Caskett fanfic called "Sweet December". I'd like to start posting next month, so keep a look out! :)


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